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“What a commission it is to express a future that none think imaginable! Of course this cannot be done by inventing new symbols… it means to move back into the deepest memories [of this community] and activate those very symbols that have always been the basis for contradicting the [present] consciousness.”

We investigated (i) if kissing partners share a more similar oral microbiota (tongue and saliva) than people with no intimate relationship, (ii) if self-reported kiss frequencies over the last year, the time passed after the latest kiss and the actual act of kissing influences the composition of oral microbiota, and (iii) the number of bacteria transferred by the use of marker bacteria.

(Even if you’re not a biologist, read through the Abstract and Background! It’s not too tough).

Essentially – we know that the human body has different environments that our microbiome occupies. Scientists are thinking about what roles the bacteria in our mouth, skin, and gut play in our health, what kind of bacteria live there, and how these communities change. These scientists wondered – what does kissing do to our oral microbiota?

The scientists took saliva samples before and after “an intimate kiss of 10s.” Then they extracted the DNA from these samples, sequenced it, and used the data to determine what kinds of bacteria were shared before and after the kiss.

So what I love:

1. It starts with a great, silly question. Science (and research as a whole) starts with good questions. I love that they believed that that there was something to learn from a silly question, turned it into a small project and a paper.

But, it’s pretty clear that the authors had a lot of fun with the project! Especially in their background: they qualify the importance of mouth-to-mouth contact in humans in courtship, going far enough to describe: “intimate kissing involving full tongue contact and saliva exchange.”

2. It highlights the complexity of the issue – we aren’t even able to answer what seems on the surface like a relatively simple question in a clear way. The paper emphasizes that while bacterial exchange does happen the most “in couples with relatively high intimate kiss frequencies,” it doesn’t tell us much about what those bacteria are, what they do, or why they grow well. It also doesn’t tell us where the bacteria colonize (tongue, teeth, or other), or how long they actually manage to last (because the samples only reflect bacterial exchange immediately after a kiss). They make sure to emphasize that there’s a lot of factors that lead to sharing microbes, like being part of the same household, or

3. The work the authors put in is very clear! From the methods section: They chose an easy to set up experiment to gather data (just kiss someone and spit in a tube!) and a simple sequencing method (16S for just bacteria) to analyze it. In this case, simplicity is the mark of a good project: they put a lot of thought in before executing so that everything would run (relatively) smooth and they can get the paper out.

They clearly answered what they learned while identifying what they wouldn’t be able to learn from this project. The answers: 1) partners have more similar oral microbiota compared to unrelated individuals. 2) intimate kissing didn’t make partners’ oral microbiota more similar. 3) using markers, there’s an average total bacterial transfer of 80 million bacteria per intimate kiss of 10s.

So, in the least scientific way possible, these authors went to a local Zoo, found 21 random couples, and asked them to make out, for science!And got an author credit, along with valuable experiences with dealing with simple metagenomic data (which, speaking from experience, is just as valuable).